Typical dynamic cryogenic seals use either a plastic jacket with a mechanical spring to energize the seal or a plastic coating on a mechanical seal. These are limited in life due to the high loads resulting from coefficient of thermal expansion (CTE) mismatch of the plastic and metallic parts, or the plastic coatings wear off with motion.
While many efforts have been made to improve plastic cryogenic seals, the state of the art designs all suffer from rolling or sliding of the weak plastic parts as the dynamic surfaces pass by. Metallic parts wear the plastic coating off after several cycles.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improved dynamic cryogenic seal design.